Comparative environmental sustainability study of an improved sewage sludge treatment and sludge reuse system based on emergy analysis in China

As the significant residuals in the sewage treatment system, sludge treatment and reuse play a pivotal impact on the environmental sustainability study in China. In this paper, two sewage sludge treatment systems have been investigated, calculated, and analyzed, including the conventional treatment system (Scenario A) and improved reuse system (Scenario B), respectively. The results demonstrate that (1) Compared to Scenario A, Scenario B is a comprehensive system, which integrates a sewage sludge treatment system and a brick production system for sludge recycling. (2) After considering the brick system (scenario B), on the one hand, the sludge treatment capacity has been enhanced and raised sludge utilization; on the other hand, negative influences have also generated due to the non-renewable resources input and several outputs. (3) In Scenario A and Scenario B, the input resources part reflects the main impact (about 59.6% in the entire emergy value). (4) In this new paper, the UEVs are 2.73E + 11sej/kg and 6.29E + 11sej/kg in Scenario A and Scenario B, respectively. (5) The emergy sustainability indexes (ESI) are 0.012292 and 0.00848, which express the weak comprehensive effects in Scenario A and Scenario B. (6) Scenario B has a more extensive range of change than Scenario A because of the more resource input for the sensitivity analysis. Given the all discussions, there are two effective approaches to be used for perfecting environmental sustainability in the Scenario A system and Scenario B system.

Environmental Sustainability Assessment of a New Sewage Treatment Plant in China Based on Infrastructure Construction and Operation Phases Emergy Analysis

Due to excessive resource consumption and pressing environmental issues of the sewage treatment industry, there is extensive attention in China. Given the unique craft production process in the sewage treatment system, a series of integral emergy indicators have been used to evaluate the environmental sustainability based on infrastructure construction and operation stage emergy analysis. Taking a new typical sewage treatment plant as an example, this paper performed a case study. The results illustrate that (1) the infrastructure construction process emergy (approximate 92.6%) is more critical than sewage treatment process emergy; (2) nonrenewable resource is the primary factor for the emergy analysis, followed by energy (23.5%) and purchased supply (7%); (3) cement, steel, and gravel have dominant impacts on the nonrenewable resource emergy; (4) the emergy sustainability index is 0.001101, which displays weak environmental sustainability; (5) the unit emergy value (UEV) of the new sewage treatment plant is 3.40 × 1012 sej/m3; (6) sensitivity analysis results of the hypothesis demonstrate that nonrenewable resources have significant fluctuations (6.903%) while, for the indicators, emergy sustainability index (ESI) (4.8072%) has the most significant impact; and (7) wastewater is a major contributor. In light of comprehensive discussions, two positive measures are proposed in order to ameliorate the environmental sustainability.

Emergy-Based Sustainability Analysis of an Ecologically Integrated Model with Maize Planting for Silage and Pig-Raising in the North China Plain

The structure of the pig-raising sector in China is changing towards large-scale and intensive systems or ecological pig-raising systems (EPRSs). To choose the best EPRS with high economic benefits and with low environmental consequences, this study combined economic analysis and emergy analysis methods to evaluate several EPRSs. Having a large percentage of maize silage in the feed (max 40%) to replace some maize increased the economic benefit and sustainability of the EPRS and decreased the pressure on the environment. The raising system that consisted of Tuhe black pigs fed feed containing maize silage (EPRS C) performed especially well. The yield-based economic profit and area-based economic profit of EPRS C increased by 37%–54% and 3%–17%, respectively, compared to those of the three-breed crossbred pig-raising systems with or without maize silage added to the feed (EPRS A and EPRS B). Its unit emergy value and emergy loading ratio were 9–22% and 10–15% lower, respectively, than those of EPRS A and EPRS B. Furthermore, its emergy yield ratio and emergy sustainability index were about 2% and 14%–19% higher, respectively, than those of EPRS A and EPRS B. To some extent, the results from EPRS C give some guidelines on improving the performance of the ecological pig-raising sector in China. Moreover, using a high concentration of maize silage in the feed and an optimal local pig type may be beneficial for the sustainability of the ecological pig-raising sector in China.

An Evaluation of Input–Output Value for Sustainability in a Chinese Steel Production System Based on Emergy Analysis

: The social investment, natural resource consumption, and pollutant emissions involved in steel production can be evaluated comprehensively using the emergy analysis. We explored the sustainability of the steel production system from four aspects: input index, output index, input–output index, and sustainability index. The results showed that the maximum inputs were the intermediate product/recyclable materials produced within the production line; energy sources were mainly non-renewable and the emergy value of pollutants discharged was rather low. The environmental load rate of the pelletizing and sintering processes were the highest and the proportion of recycled materials for puddling and steel-making were the highest. The emergy investment rate of rolling was the highest; the emergy value of the pollutants discharged in each process was very small, and the emergy yield ratio was highest in the rolling process. Pelletizing, sintering, and steel-making were input consuming processes, but the sustainability index of puddling and rolling processes was sound. The whole process line can be sustainable, considering the useful intermediate and recyclable products.

Agro-ecological compensation of watershed based on emergy

The paper aims at providing a framework to calculate the agro-eco-compensation standard based on the systems agro-ecological concept of embodied energy as emergy. We have proposed a calculation system of eco-compensation standard for sustainable agricultural development based on the convertibility between emergy and price. According to our calculation, the total energy of agricultural production in Yongding River Basin was 3.45 E + 16 Sej/ha (the unit emergy value, expressed in solar emergy joules per unit) in terms of the renewable resources, nonrenewable resources, material inputs, and service costs. The energy of renewable and nonrenewable resources was 1.59 E + 16 and 1.86E + 16 Sej/ha, respectively. The ESI (environmental sustainability index) of the study area was 0.1056, indicating that its agricultural production was in a seriously unsustainable condition. To realize the sustainable agricultural production in the watershed, the downstream governments should pay $21.81 M (¥135 million) approximately to upstream governments for water and soil conservation. The results of the present study suggested that the emergy-based calculation method of agro-eco-compensation standard is feasible to a certain degree.

The Emergy Value Assessment of Municipal Waste Management in Yogyakarta, Indonesia

The emergy values of three different scenarios for the new landfill in Yogyakarta City were calculated to evaluate the sustainability and efficiency. The assessment included the environmental parameters which are Environmental Yield Ratio (EYR), Net Emergy, Environmental Loading ratio (ELR) and Emergy Sustainability Index (ESI).The calculation of emergy indices showed that treatment in landfill requires the largest emergy input for all scenarios with the percentage between 92% and 97%. Scenario 0 contains the lowest total solar emergy implying that it requires lower emergy input compared to other scenarios. Scenario 1 needs the lowest emergy investment. Meanwhile, Scenario 2 offers the highest emergy recovery contributed mainly by the output from higher scavenging rate. Scenario 2 is the best option for the municipal waste management in Yogyakarta since it meets more criteria for sustainability and efficiency.